Github access is mostly intended for use by developers, but users can also
access the MapServer source between releases as it is being developed. Github
access is only recommended for those who need the absolute latest and greatest
code, if they are not afraid of getting their hands dirty building the source.
The Github repository does not contain GD or
any of the support libraries, and it requires flex and bison to build it.
Building MapScript will also require SWIG be
installed on your machine. Here’s how to access the source:

If you find yourself submitting a lot of push requests to GitHub, or you would
like to be an active developer that picks up the maintenance of a portion of MapServer,
contact Steve Lime, one of the other developers, or send a message to the MapServer-dev Listat e Postimit.
To obtain GitHub commit/push access, an individual must:

demonstrate expertise about a specific area

be willing to put more time into the project than just the short term
(dumping code into the project and providing no way to maintain it is almost
as bad as having no code at all)